1. Field of the Invention
The present invention generally relates to a power converter, and more particularly, to a pulse width modulation (PWM) signal controlling apparatus of a power converter.
2. Description of Related Art
Power converters have been provided for supplying different operation powers to different electronic products along with the diversification of today's electronic products. A power converter switches a power transistor switch according to a pulse width modulation (PWM) signal for achieving a power converting action.
A PWM signal is usually generated by a PWM signal controlling apparatus. Since a PWM signal controlling apparatus is usually implemented as an integrated circuit (IC), additional pins for receiving additional input signals have to be disposed in order to accomplish new functions in the PWM signal controlling apparatus. These additional pins of the PWM signal controlling apparatus take up a lot of surface area in the circuit layout of the IC and accordingly increase the circuit cost. In addition, with the increased number of pins, the packaging type of the integrated PWM signal controlling apparatus may have to be changed, and as a result, the circuit board carrying the PWM signal controlling apparatus may have to be changed correspondingly. In other words, many troublesome engineering issues may arise from these additional pins.